1. Field of the Invention
The present invention relates generally to electrical switchgear and more particularly to an insulating barrier system for switchgear; the barrier system being easily removable from and insertable into the switchgear.
2. Description of the Related Art
Various types of electrical switchgear, for example, operating in the range of 4000 to 35,000 volts, utilize barriers fabricated from insulating material that are positioned between the components of adjacent electrical phases. These barriers, which are referred to as interphase barriers and end barriers, provide desired insulation between energized parts of different phases and between energized parts and ground. The barriers also provide physical separation and isolation between phases and between energized parts and ground to facilitate such operations as fuse handling.
The components mounted in the switchgear include switches and fuses. The switches and fuses include circuit connection points which are required to be connected to underground cables or wires using various forms of cable terminations. To accomplish the cable terminations at the connection points, the cables coming from below the switchgear enclosure are manipulated to enter the open bottom of the enclosure and are routed for termination to the connection points of the components.
With the barriers fixed in place, it is difficult in the space between the barriers to prepare the cables for connection to the switchgear as this entails stripping insulation from the cables, installing connectors, and installing the terminators. It is also relatively difficult to provide optimum placement and orientation of the cables to take account of electrical considerations for the prevention of tracking and for maintaining the dielectric properties and withstand voltage of the switchgear. Removal of the barriers aids the efficiency of preparing the cables for connection, and also permits more desirable placement and orientation of the cables with respect to the components and barriers.
Additionally, it is often desirable to remove the barriers to perform cleaning of the components of the switchgear. When the switchgear is cleaned while deenergized, the procedures typically require removal of the barriers to give access to the components. For energized cleaning, an insulated wand is utilized to spray small particles and the barriers generally do not inhibit the cleaning procedures. However, in some cases, it still may be considered desirable to remove the barriers to permit greater accessibility of the wand to the components during such energized cleaning.
Thus, it is desirable to remove the barriers when performing the cable terminations and when cleaning the switchgear. However, many types of commercially available switchgear, for example, as shown in S&C Electric Company Descriptive Bulletin 662-30 issued on Sept. 8, 1986, utilize barriers that are fastened and/or clamped at one or more locations to the switchgear enclosure or to members attached to the enclosure. For example, each of the interphase barriers is bolted at the upper front portion, is clamped at the lower rear portion, and in some cases is also clamped at the upper rear portion. Removal of these barriers entails the relatively time-consuming disassembly of the hardware that retains the barriers. There is also the possibility of losing the hardware while the work in the gear is being performed and before the barriers are reassembled into the switchgear. Additionally, the barriers are relatively difficult to reinsert and assemble into the switchgear since the worker must either reach into the gear about three feet to assemble a clamp or other fasteners, or very accurately guide the barriers into a guide or a clamp. Of course, this cannot be safely accomplished with the switchgear energized. The possibility also exists of incorrectly positioning the barriers in the switchgear, which can reduce the stability of the barriers and the withstand voltage of the switchgear and may even encourage tracking across the barrier. For example, the barrier may be incorrectly positioned such that it contacts a cable or an energized component.
Another type of switchgear, available from Electrical Equipment Inc., Birmingham, Ala., utilizes a three-phase removable barrier system including two interphase barriers and two end barriers which are fixedly assembled into a single assembly by tubular support members or spacers. The three-phase barrier assembly includes extending flanges. The enclosure is provided with internally extending ledges along each side of each compartment. The flanges of the barrier system rest on top of the ledges of the enclosure to support the barrier assembly. When the barrier assembly is inserted or removed from the enclosure, the flanges slide on the ledges to guide the barrier assembly, as well as support the rather considerable weight of the barrier assembly. The enclosure also includes a horizontal guide member located at the lower rear of each compartment. Upon insertion of the barrier assembly, the barriers engage the receiving notches of the guide member. While this removable barrier assembly may avoid the removal and loss of hardware when the barriers are removed and prevent improper positioning of the barriers in the switchgear, the insertion or removal of the barrier assembly is difficult to perform by one individual due to the rather considerable weight and volume of the barrier. For example, the dimensions of the barrier assembly approximate a cube three feet on a side. Additionally the barrier assembly is subject to damage and/or distortion during handling and during the time it is outside the switchgear. For example, any distortion of a barrier with respect to the overall assembly may result in improper barrier positioning when the barrier assembly is inserted into the switchgear.
Thus, none of these barrier arrangements is capable of being easily removed or inserted. As a result, much valuable time is lost by personnel in attempting to make desirable cable terminations and to clean the components in the gear.